The present invention relates to an improvement in a starting decompression device for four-cycle engines, which in effecting cranking for starting the engine manually by use of a kick pedal, a starter rope or the like, can forcedly open an exhaust valve to decompress the interior of a combustion chamber for facile achievement of cranking.
Such devices as known are designed so that the exhaust valve of the engine is forcedly opened by opertion of a swing arm. However, in the present invention, the swing arm must be returned to release a force opening of the exhaust valve at the proper time when rotation of the crank shaft is accelerated during the cranking of the engine. However, such a return operation is cumbersome and requires skill to be accomplished.
In view of the foregoing, the present invention has as its object the provision of a device as described above, which is simple and easy to operate and is simply built, wherein a cam member is used to forcedly open an exhaust valve, and the cam member is automatically operated for return at a suitable time during cranking to close the exhaust valve, thus reducing the initial load of cranking and positively starting the engine.
Other objects and features of the invention will become apparent from the following description and claims, as illustrated in the accompanying drawings.